3D Memory Etch-Stop Structure for Density and Complexity

Solution Overview

Problem

The challenge is to develop a 3D memory device with increased memory density and reduced size, while overcoming the complexity and reliability issues arising from the shrinkage of critical sizes in multi-layer stacks, which leads to program/erase interference between adjacent memory cells.

Innovation Solution

A 3D memory device is designed with a substrate having a trench and a multi-layer stack with alternating conductive and insulating layers, featuring a first extending portion and a second extending portion forming a non-straight angle with the trench bottom, along with an etching stop structure made of the same material as the memory structure, allowing for reduced device size and simplified manufacturing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the critical size of the multi-layer stack is shrunk to provide larger memory density, then memory density is improved, but manufacturing complexity increases and reliability deteriorates due to program/erase interference

Engineering Contradiction:

Improvememory densityVSAvoidmanufacturing complexity

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The multi-layer stack is segmented into two extending portions (first and second extending portions) that form a non-straight angle with the trench bottom. This segmentation allows the stack to be divided into functional regions, with the etching stop structure selectively positioned in the second extending portion, thereby simplifying the manufacturing process while maintaining high memory density.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

An etching stop structure is introduced as an intermediary element within the multi-layer stack. This etching stop structure, having material identical to the memory structure, serves as a mediator that prevents program/erase interference between adjacent memory cells while maintaining the shrunk critical size for high memory density.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Quantity of substance

If the critical size of the multi-layer stack is shrunk to provide larger memory density, then memory density is improved, but reliability deteriorates due to program/erase interference between adjacent memory cells

Engineering Contradiction:

Improvememory densityVSAvoiddata storage reliability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The multi-layer stack is segmented into two extending portions (first and second extending portions) that form a non-straight angle with the trench bottom. This segmentation allows the stack to be divided into functional regions, with the etching stop structure selectively positioned in the second extending portion, thereby simplifying the manufacturing process while maintaining high memory density.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

An etching stop structure is introduced as an intermediary element within the multi-layer stack. This etching stop structure, having material identical to the memory structure, serves as a mediator that prevents program/erase interference between adjacent memory cells while maintaining the shrunk critical size for high memory density.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If a conventional staircase contact structure is used to connect word lines, then electrical connection is achieved, but device surface area is occupied and size increases

Engineering Contradiction:

Improveelectrical connectionVSAvoiddevice surface area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent transitions from a conventional planar staircase contact structure to a vertical multi-layer stack architecture. Word lines are connected through vertical conduits and contact structures that extend through multiple layers, utilizing the third dimension (vertical space) to achieve electrical connections without occupying additional device surface area.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The contact structures and word line connections are nested within the vertical multi-layer stack structure. The etching stop structure and memory structures are positioned within the trench, with conductive layers and insulating layers alternatively stacked, creating a nested configuration that eliminates the need for external staircase contact structures.

Inventive Principle:

Principle #7Nested doll (Nesting)

Data Source

PatentUS10497714B2Three dimensional memory device with etch-stop structure

Publication Date: 2019.12.03 MACRONIX INTERNATIONAL CO LTD

AI summary

A 3D memory device includes a substrate, a multi-layers stack, at least one memory structure and an etching stop structure. The substrate has a trench. The multi-layers stack includes a first extending portion forming a non-straight angle with a bottom surface of the trench and a second extending portion, wherein both of the first extending portion and the second extending portion include a plurality of conductive layers and a plurality of insulating layers alternatively stacked in the trench. The memory structure is formed in the first extending portion. The etching stop structure is at least partially disposed in the second extending portion and has a material identical to that of the memory structure.